1. Field of the Invention
The present invention relates to an improvement in a method for roughening a surface of a semiconductor, in particular, a gallium nitride semiconductor.
2. Description of the Related Art
In a light emitting diode (LED), a PN junction 14 formed from an N type layer 10 and a P type layer 12 is used as the light emitting section, as shown in FIG. 1(a). The light emitted from the light emitting section is extracted for use in various applications. In such an LED, the surface of the element is usually formed flat. When the surface of the LED is flat, a large portion of the light emitted from the PN junction 14 is reflected at the surface of the LED, as shown in FIG. 1(a), and is not emitted to the outside. Because of this, there had been a problem in that the light extraction efficiency cannot be increased.
In order to solve this problem, it is effective to roughen the surface for extracting light of the semiconductor which constitutes the LED, as shown in FIG. 1(b). When a surface of the semiconductor constituting the LED is roughened, reflection, at the light extraction surface of the semiconductor, of the light generated at the PN junction 14 back to the inside of LED when the light reaches the light extraction surface can be avoided, as shown in FIG. 1(b). This facilitates extraction of light to the outside of the LED and the light extraction efficiency of the LED can be improved.
Moreover, when the surface of the semiconductor constituting the LED is roughened, the surface area is significantly increased compared to a flat surface. This facilitates ohmic contact and thus, formation of an electrode.
However, conventionally, there had been no method for easily roughening the surface of the semiconductor constituting the LED.